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WO2010068169A1 - Method for producing cemented carbide products - Google Patents

Method for producing cemented carbide products Download PDF

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Publication number
WO2010068169A1
WO2010068169A1 PCT/SE2009/051393 SE2009051393W WO2010068169A1 WO 2010068169 A1 WO2010068169 A1 WO 2010068169A1 SE 2009051393 W SE2009051393 W SE 2009051393W WO 2010068169 A1 WO2010068169 A1 WO 2010068169A1
Authority
WO
WIPO (PCT)
Prior art keywords
core
feedstock
cemented carbide
parts
wax
Prior art date
Application number
PCT/SE2009/051393
Other languages
French (fr)
Inventor
Mattias Puide
Original Assignee
Seco Tools Ab
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Seco Tools Ab filed Critical Seco Tools Ab
Publication of WO2010068169A1 publication Critical patent/WO2010068169A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C33/00—Moulds or cores; Details thereof or accessories therefor
    • B29C33/44—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles
    • B29C33/52—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles soluble or fusible
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/22—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip
    • B22F3/225—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip by injection molding
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/04—Making non-ferrous alloys by powder metallurgy
    • C22C1/05—Mixtures of metal powder with non-metallic powder
    • C22C1/058—Mixtures of metal powder with non-metallic powder by reaction sintering (i.e. gasless reaction starting from a mixture of solid metal compounds)
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
    • C22C29/02—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides
    • C22C29/06—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds
    • C22C29/08—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds based on tungsten carbide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2999/00—Aspects linked to processes or compositions used in powder metallurgy

Definitions

  • the present invention relates to a method for the production of tungsten carbide based hard metal tools or compo- nents using the powder injection moulding method.
  • Hard metals based on tungsten carbide are composites consisting of small ( ⁇ m-scale) grains of at least one hard phase in a binder phase. These materials always contain the hard phase tungsten carbide (WC) .
  • tungsten carbide WC
  • other metal carbides with the general composition (Ti, Nb, Ta, W) C may also be included, as well as metal carbonitrides, e.g., Ti(C 7 N) .
  • the binder phase usually consists of cobalt (Co) .
  • Other binder phase compositions may also be used, e.g., combinations of Co, Ni, and Fe, or Ni and Fe.
  • Industrial production of tungsten carbide based hard metals often includes blending of given proportions of powders of raw materials and additives in the wet state using a mill- ing liquid.
  • This liquid is often an alcohol, e.g. ethanol or water, or a combination thereof.
  • the mixture is then milled into homogeneous slurry.
  • the wet milling operation is made with the purpose of deagglomeration and mixing the raw materials intimately. Individual raw material grains are also disintegrated to some extent.
  • the obtained slurry is then dried and granulated, e.g. by means of a spray dryer.
  • the granulate thus obtained may then be used in uniaxial pressing of green bodies or for extrusion or injection moulding.
  • Injection moulding is common in the plastics industry, where material containing thermoplastics or thermosetting polymers are heated and forced into a mould with the desired shape.
  • the method is often referred to as Powder In- jection Moulding (PIM) when used in powder technology.
  • PIM Powder In- jection Moulding
  • the method is preferably used for parts with complex geometry. In powder injection moulding of tungsten carbide based hard metal parts, four consecutive steps are applied:
  • IA Mixing of the granulated cemented carbide powder with a binder system.
  • the binder system acts as a carrier for the powder and constitutes 25-60 volume % of the resulting material, often referred to as the feedstock.
  • the exact concentration is dependent on the desired process properties during moulding.
  • the mixing is made by adding all the con- stituents into a mixer heated to a temperature above the melting temperature of the organic binders .
  • the resulting feedstock is obtained as pellets of approximate size 4x4 mm.
  • Injection moulding is performed using the mixed feedstock.
  • the material is heated to a temperature where the organic constituents are molten and the feedstock is viscous and thereby processable with a common injection moulding machine.
  • the viscous feedstock is then forced into a cavity with the desired shape.
  • the thus obtained part is solidified by cooling or curing and then removed from the cavity.
  • Removing the binder from the obtained part can be obtained by extraction of the parts in a suitable solvent and/or by heating in a furnace with a suitable atmosphere. This step is often referred to as the debinding step.
  • the PIM process is preferably used for parts with complex geometry.
  • One advantage is the possibility is to produce parts with cavities for use as cooling channels, structures for connecting the cemented carbide part with another part, e.g. a cutting tool holder or to save expensive cemented carbide material .
  • Injection moulding of hollow parts require a core inside the mould.
  • the feedstock is injected in the cavity around the core to mould the part.
  • the core is removed and the mould is opened, revealing the part.
  • the core can be solid or of collapsing type.
  • a release angle of about I 2 is sufficient to remove the core without distorting the part.
  • collapsible cores can be used. Collapsible cores can only collapse slightly before being removed from the. part.
  • collapsible cores use intriguous mechanics to be able to collapse, smaller collapsible cores than about 10 mm in diameter are too sensitive and expensive to be of practical use.
  • Another drawback with the collapsible cores is that they can only collapse slightly, making them unusable for hollow parts with large undercuts.
  • Figure 1 shows an example of a core according to the present invention.
  • the core is made by a paraffin wax with a relatively high melting point, i.e. in the range of 100-120 2 C, preferably a Fischer-Tropsch wax.
  • the core melting temperature shall be higher than the melt temperature of the feedstock according to step 1.
  • a suitable melt temperature of the feedstock is in the range of 70-95 2 C, preferably 70-80 2 C.
  • Removing the core by dissolving from part This can be made together with the solvent extraction of the binder in step 6B. It is also possible to dissolve the core insert before or after the solvent extraction of the organic binder.
  • the core may be removed by dissolving with a nonpo- lar solvent, e.g. carbondioxide at supercritical physical conditions, n-hexane or any other aliphatic alkane.
  • the invention can be used for all compositions of cemented carbide and all WC grain sizes commonly used as well as for titanium carbonitride based materials.
  • a WC-13 wt-% Co submicron cemented carbide powder was made by wet milling 780 g Co-powder (OMG extra fine), 38.66 g
  • the stearic acid is added in this stage of the process to work as a granule forming agent, when spray drying the slurry.
  • the resulting slurry was spraydried to a granulated powder .
  • the powder was mixed by kneading 2500 g powder with 50.97 g Polypropylene wax (Clariant Licocene PP 1302) and 50.97 g Paraffin wax (Sasol Wax) in a Z-blade kneader mixer (Werner & Pfleiderer LUK 1,0) .
  • the Z-blade kneader was heated to 100 ° C and the raw material was added.
  • the mixer was run until a smooth viscous feedstock developed. This resulted in a feedstock with a melt temperature of 80 2 C.
  • Cores for the production of a central cooling channel combined with two bent cooling channels (Figure 1) were made by injection moulding.
  • the cores were placed inside a mould (Seco Tools Minimaster size 12mm) and the feedstock was injection moulded around the wax core at 80 2 C. When the part had solidified by cooling, the part with the core was removed from the cavity.
  • the parts were placed in an equipment for extraction with carbon dioxide at supercritical physical conditions .
  • the extraction process was run at 35 MPa and 55 2 C for 20 hours.
  • the parts were sintered in a Sinter-HIP furnace (PVA COD733R) at 1420 0 C with a total soaking time of 60 min. After 30 min at the peak hold temperature, the furnace pressure was raised to 3 MPa Ar.
  • PVA COD733R Sinter-HIP furnace
  • the parts from example 5 were free from carbon pores, cracks, eta-phase and pores, i.e. AOO BOO COO according to ISO 4505.
  • the cooling channel had the desired shape.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Manufacturing & Machinery (AREA)
  • Powder Metallurgy (AREA)

Abstract

The present invention relates to a method of making a hollow body of cemented carbide or cermet by injection molding technique from a feedstock using a core to form the hollow-part of the body. According to the invention the core is made of a material that can be dissolved in a solvent and the core melting temperature is higher than the melting temperature of the feedstock.

Description

Method for producing cemented carbide products
The present invention relates to a method for the production of tungsten carbide based hard metal tools or compo- nents using the powder injection moulding method.
Hard metals based on tungsten carbide are composites consisting of small (μm-scale) grains of at least one hard phase in a binder phase. These materials always contain the hard phase tungsten carbide (WC) . In addition, other metal carbides with the general composition (Ti, Nb, Ta, W) C may also be included, as well as metal carbonitrides, e.g., Ti(C7N) . The binder phase usually consists of cobalt (Co) . Other binder phase compositions may also be used, e.g., combinations of Co, Ni, and Fe, or Ni and Fe.
Industrial production of tungsten carbide based hard metals often includes blending of given proportions of powders of raw materials and additives in the wet state using a mill- ing liquid. This liquid is often an alcohol, e.g. ethanol or water, or a combination thereof. The mixture is then milled into homogeneous slurry. The wet milling operation is made with the purpose of deagglomeration and mixing the raw materials intimately. Individual raw material grains are also disintegrated to some extent. The obtained slurry is then dried and granulated, e.g. by means of a spray dryer. The granulate thus obtained may then be used in uniaxial pressing of green bodies or for extrusion or injection moulding.
Injection moulding is common in the plastics industry, where material containing thermoplastics or thermosetting polymers are heated and forced into a mould with the desired shape. The method is often referred to as Powder In- jection Moulding (PIM) when used in powder technology. The method is preferably used for parts with complex geometry. In powder injection moulding of tungsten carbide based hard metal parts, four consecutive steps are applied:
IA. Mixing of the granulated cemented carbide powder with a binder system. The binder system acts as a carrier for the powder and constitutes 25-60 volume % of the resulting material, often referred to as the feedstock. The exact concentration is dependent on the desired process properties during moulding. The mixing is made by adding all the con- stituents into a mixer heated to a temperature above the melting temperature of the organic binders . The resulting feedstock is obtained as pellets of approximate size 4x4 mm.
2A. Injection moulding is performed using the mixed feedstock. The material is heated to a temperature where the organic constituents are molten and the feedstock is viscous and thereby processable with a common injection moulding machine. The viscous feedstock is then forced into a cavity with the desired shape. The thus obtained part is solidified by cooling or curing and then removed from the cavity.
3A. Removing the binder from the obtained part. The removal can be obtained by extraction of the parts in a suitable solvent and/or by heating in a furnace with a suitable atmosphere. This step is often referred to as the debinding step.
4A. Sintering of the parts. Common sintering procedures for cemented carbides are applied.
The PIM process is preferably used for parts with complex geometry. One advantage is the possibility is to produce parts with cavities for use as cooling channels, structures for connecting the cemented carbide part with another part, e.g. a cutting tool holder or to save expensive cemented carbide material .
Injection moulding of hollow parts require a core inside the mould. The feedstock is injected in the cavity around the core to mould the part. When the feedstock has solidified by cooling or curing, the core is removed and the mould is opened, revealing the part. The core can be solid or of collapsing type. When the core is solid, there must not be any undercuts in the direction in which the core is removed. Usually, a release angle of about I2 is sufficient to remove the core without distorting the part. In cases when it is not possible to design the moulding tooling without undercuts or to provide a sufficient release angle, collapsible cores can be used. Collapsible cores can only collapse slightly before being removed from the. part. Since the collapsible cores use intriguous mechanics to be able to collapse, smaller collapsible cores than about 10 mm in diameter are too sensitive and expensive to be of practical use. Another drawback with the collapsible cores is that they can only collapse slightly, making them unusable for hollow parts with large undercuts.
It is an object of the present invention to solve these problems .
Figure 1 shows an example of a core according to the present invention.
According to the invention, by making the core of a material that can be dissolved in the same solvent as the one being used for the binder removal by extraction or a different solvent before or after the binder removal, these problems can be solved. Such a process comprises the fol- lowing steps :
IB. Providing a feedstock according to step IA above. 2B. Shaping the core with a material that is possible to dissolve in a solvent that does not dissolve or in any- other way affect the hard constituents of the feedstock made in step 1. The shaping can be made by, but is not limited to, injection moulding or casting. In one embodiment, the core is made by a paraffin wax with a relatively high melting point, i.e. in the range of 100-120 2C, preferably a Fischer-Tropsch wax. The core melting temperature shall be higher than the melt temperature of the feedstock according to step 1. A suitable melt temperature of the feedstock is in the range of 70-95 2C, preferably 70-80 2C.
3B. Placing the core in the mould.
4B. Performing injection moulding using the mixed feedstock. The material is heated to a temperature below the melting point of the core, but high enough to make the feedstock viscous, and is then forced into the cavity in the mould and around the core. The thus obtained part is cooled and then removed with the core from the mould cavity.
5B. Removing the core by dissolving from part. This can be made together with the solvent extraction of the binder in step 6B. It is also possible to dissolve the core insert before or after the solvent extraction of the organic binder. The core may be removed by dissolving with a nonpo- lar solvent, e.g. carbondioxide at supercritical physical conditions, n-hexane or any other aliphatic alkane.
6B . Removing the binder from the obtained part . The removal can be obtained by extraction of the parts in a suitable solvent and/or by heating in a furnace with a suitable at- mosphere . 7B. Presintering of the part in the debinding furnace in vacuum at 900-1250 0C, preferably at about 1200 0C.
8B. Sintering of the parts using conventional sintering technique .
With the method according to the invention, it is possible to produce hollow PIM-parts with smaller and geometrically more complex cavities than the prior art methods with col- lapsing or solid cores. Cores with a diameter less than 2 mm and high mechanical complexity are possible, since the core is removed by dissolving in-situ.
The invention can be used for all compositions of cemented carbide and all WC grain sizes commonly used as well as for titanium carbonitride based materials.
Example
A WC-13 wt-% Co submicron cemented carbide powder was made by wet milling 780 g Co-powder (OMG extra fine), 38.66 g
Cr3C2 (H.C.Starck) , 5161 g WC (H.C.Starck DS80) , 20.44 g W metal powder and 22 g stearic acid in 1.6 1 milling liquid consisting of ethanol and water (80:20 by weight) for 40 h.
The stearic acid is added in this stage of the process to work as a granule forming agent, when spray drying the slurry. The resulting slurry was spraydried to a granulated powder .
The powder was mixed by kneading 2500 g powder with 50.97 g Polypropylene wax (Clariant Licocene PP 1302) and 50.97 g Paraffin wax (Sasol Wax) in a Z-blade kneader mixer (Werner & Pfleiderer LUK 1,0) . The Z-blade kneader was heated to 100°C and the raw material was added. The mixer was run until a smooth viscous feedstock developed. This resulted in a feedstock with a melt temperature of 802C. Cores for the production of a central cooling channel combined with two bent cooling channels (Figure 1) were made by injection moulding. It is not possible to make a cavity in cemented carbide with this shape with conventional meth- ods . The cores were injection moulded with a conventional injection moulding machine using a Fischer-Tropsch wax (Sasol Wax Hl) with a melting point of 110sC.
The cores were placed inside a mould (Seco Tools Minimaster size 12mm) and the feedstock was injection moulded around the wax core at 802C. When the part had solidified by cooling, the part with the core was removed from the cavity.
The parts were placed in an equipment for extraction with carbon dioxide at supercritical physical conditions . The extraction process was run at 35 MPa and 552C for 20 hours.
The parts were sintered in a Sinter-HIP furnace (PVA COD733R) at 1420 0C with a total soaking time of 60 min. After 30 min at the peak hold temperature, the furnace pressure was raised to 3 MPa Ar.
After sintering, the parts were cut for inspection. The parts from example 5 were free from carbon pores, cracks, eta-phase and pores, i.e. AOO BOO COO according to ISO 4505. The cooling channel had the desired shape.

Claims

Claims
1. Method of making a hollow body of cemented carbide or cermet by injection molding technique from a feedstock us- ing a core to form the hollow part of the body c h a r a c t e r i s e d in that the core is made of a material that can be dissolved in a solvent the core melting temperature being higher than the melting temperature of the feedstock.
2. Method according to claim 1, c h a r a c t e r i s e d in that the core is made of a paraffin wax with a relatively high melting point, i.e. in the range of 100-120 2C
3. Method according to claim 2 , c h a r a c t e r i s e d in that the wax is a Fischer-Tropsch wax.
4. Method according to any of the preceding claims c h a r a c t e r i s e d in that the melt temperature of the feedstock is in the range of 70-95 2C, preferably 70-80 3C.
PCT/SE2009/051393 2008-12-11 2009-12-09 Method for producing cemented carbide products WO2010068169A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE0802550 2008-12-11
SE0802550-4 2008-12-11

Publications (1)

Publication Number Publication Date
WO2010068169A1 true WO2010068169A1 (en) 2010-06-17

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4904423A (en) * 1983-03-28 1990-02-27 Park Chemical Company Pressure molding process using salt cores and composition for making cores
WO1993017820A1 (en) * 1992-03-05 1993-09-16 Abb Cerama Ab Method of removing cores during injection moulding of objects starting from metallic and/or ceramic materials in powdered state
US20020038923A1 (en) * 2000-10-04 2002-04-04 Alcan Technology & Management Ltd. Process for manufacturing components of fibre-reinforced plastics
US6547210B1 (en) * 2000-02-17 2003-04-15 Wright Medical Technology, Inc. Sacrificial insert for injection molding
US20060082013A1 (en) * 2004-10-19 2006-04-20 Clariant Gmbh Process for production or treatment of hollow articles

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4904423A (en) * 1983-03-28 1990-02-27 Park Chemical Company Pressure molding process using salt cores and composition for making cores
WO1993017820A1 (en) * 1992-03-05 1993-09-16 Abb Cerama Ab Method of removing cores during injection moulding of objects starting from metallic and/or ceramic materials in powdered state
US6547210B1 (en) * 2000-02-17 2003-04-15 Wright Medical Technology, Inc. Sacrificial insert for injection molding
US20020038923A1 (en) * 2000-10-04 2002-04-04 Alcan Technology & Management Ltd. Process for manufacturing components of fibre-reinforced plastics
US20060082013A1 (en) * 2004-10-19 2006-04-20 Clariant Gmbh Process for production or treatment of hollow articles

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